<!DOCTYPE html>
<html class="reftest-wait">
<title>
Removing CSS animation in delay phase destroys stacking context
</title>
<style>
span {
  height: 100px;
  width: 100px;
  position: fixed;
  background: green;
  top: 50px;
}
@keyframes TransformNone {
  from, to { transform: none }
}
#test {
  width: 100px; height: 100px;
  background: blue;
  transform: none ! important;
}
</style>
<span></span>
<div id="test"></div>
<script>
window.addEventListener("load", () => {
  var target = document.getElementById("test");
  target.style.animation = "TransformNone 100s 100s";

  // We need to wait for MozAfterPaint instead of requestAnimationFrame to
  // ensure the stacking context has been updated on the compositor.
  window.addEventListener("MozAfterPaint", function firstPaint() {
    window.removeEventListener("MozAfterPaint", firstPaint, false);
    // Here we have CSS animation on transform:none style element, so
    // there should be a stacking context.

    target.style.animation = "";
    // This time we don't need to wait for MozAfterPaint because reftest tool
    // will be received MozAferPaint event.
    requestAnimationFrame(() => {
      // Now we have only transform:none style, so we should not create any
      // stacking context.
      document.documentElement.classList.remove("reftest-wait");
    });
  }, false);
});
</script>
